Aircraft engine synchronizing system



Jan. 5, 1937; W. s. BERRY z fi v AIRCRAFT ENGINE SYNCHRONIZING SYSTEM Filed April 17, 1935 2 Sheets-Sheet l MASTER INVENTOR.

Y W/'///'am S. Ber/7 ATTORN EY.

Jam. 5, 1937. A w s BERRY $066319 AIRCRAFT ENGINE SYNCHRONIZ ING SYSTEM Filed April 17, 1935 2 Sheets-Sheet 2 INVENTOR.

v Patented Jan. 5,; 1937 PATENT OFFICE AIRCRAFT ENGINE simorrrtomzmo SYSTEM William S. Berry, Hagerstown, Md, assignor to Pioneer Instrument Company, Inc., Brooklyn,

N. Y., a corporation of New York Application April 17, 1935, Serial.No..16,935

Claims. (Cl. 609'l) The present invention relates'to apparatusior electrically synchronizing the engines and propellers of a multi-engine aircraft.

One of the objects of the invention is to pro 5 vide novel electrical apparatus for automatically controlling the speed control means of a plurality of aircraft engines each driving a respective propeller, so that said propellers will rotate in fixed speed relation, i. e., so that they will rotate in synchronism.

Another object is to provide novel electrical apparatusfor automatically controlling the speed control means of a plurality of aircraft engines so that they will continuously operate in synchronis'm with a master engine the of which is controlled manually to maintain a predetermined speed whereby all of said engines will operate in fixed speed relation. 1 Another object is to provide a novel electrical an apparatus for I pellers of a multi-engine aircraft at the same predetermined speed.

Another object is to provide a novel electrical control apparatus for a. multi-engine air- 26 craft whereby the engines of the aircraft, and

hence the respective propellersthereot-are automatically maintained in synchronism. thus eliminating excessive periodical vibrations of the structure of the craft and preventing a weaken-- 30 ing thereof.

Another object of the invention is to provide a novel electrical control apparatus for the internal combustion engines of a multi-engine aircraft whereby manual operation of the individual engine throttles is rendered unnecessary to maintain the engines and their respective propellers in synchronism, thus reducing the pilot's labors and consequently increasing the safety factor in air travel.

40 A further object is to provide a novel switch mechanism inautomatic control apparatus of the class described whereby the operator or pilot may quickly and conveniently render the automatic control ineffective and resortto individual manual control of the respective engines or thepropellers driven thereby.

A still further object is to provide novel electrical apparatus for synchronizing a controlled engine of an aircraft with a master engine thereof, comprising means for. producing a pcriodicallyreversing magnetic held by the operation of one engine and reversing at a frequency corresponding to the speed or said engine, means for producing a second periodi- 'cally reversing magnetic field by the operation operation maintaining a plurality of proapplied to a three-engine aircraft.

of the other engine and reversing at a frequency corresponding to the speed of said other engine, means for combining said two fields, whereby a change in phase relation is produced between said fields when the latter are reversing 5 out of synchronism due to a difierence in speed of the two engines, and means eflective when said change in phase relation takes place, for regulating'the speed of the controlled engine-to that of the master engine. 1

Other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one embodiment of the in- 15 vention is illustrated. It is to be expressely understood, however. that the drawings are for the purposes of illustration. and description only and are not designed as a definition of the limits of the invention, referencebeing had for 2 this purpose to the appended claims.

Theinvention consists substantially in the construction, combination, location and relative arrangement of parts and electrical circuits for obtaining the results desired in accordance with '25 I the foregoing objects, as will be'more fully hereinafter set forth in the specification, as shown in the drawings, by way of example, and as finallly pointed out in the claims.

In the drawings wherein like reference char- 3o acters refer to like parts throughout the several views:

Fig. 1 is a more or less schematic view illustrating one embodiment of the invention as Fig. 2 is a. circuit diagram illustrating the manner of connecting the electrical elements of the novel combination constituting the invention;

Fig. 3 is a view in elevation illustrating one form of novel switching mechanism connected 0 to the individual speed control means of the respective aircraft engines whereby the automatic control may be rendered ineffective and the engines controlled individually by their respective speed control means; and 46 Fig. 4 is a detail section of the device l'l taken on line 4-4 of Fig. 1.

In accordance with the invention, two or more aircraft engines are synchronized by providing an alternating current generator connected to and 50 Q driven by one of the engines, which will be called the master engine, for generating an alternating current having a frequency corresponding to the speed of said master engine. At the other engine, which will be hereafter referred to as the con- 5 ary but relatively rotatable stator is electrically connected to and energized by the alternating current from the master engine the speed of which is manually controlled.

When the controlled engine is operating at the same speed as the master engine, the alternating current field in the stator is reversing at the same frequency as the field produced by the field winding which is rotated by the controlled,.engine and, therefore, no change in phase'relatlon takes place between the field of the stator and the field of the field winding as both fields are in synchronism and, hence, no relative rotation is produced between the two field windings. If, however, the speed of the controlled engine increases or decreases with respect to the speed of the master engine, a corresponding increase or decrease in the frequency of reversal of the field of the field winding with respect to the frequency of reversal of the stator field will take place thereby producing a change in phase relation which will cause the relatively rotatable stator to move angularly in one direction or another from its'normally stationary position and an amount corresponding to the magnitude of the change in phase relation between the two rotating fields. This relative rotation of the stator of the synchronous motor is employed, in accordance with the invention, to actuate the speed control means, such as the carburetor valve, of the controlled engine and, therefore, said stator is connected to said speed control means of said controlled engine and in such a manner that when the speed of the controlled engine decreases below that of the master engine, .said speed control means will be actuated to increase the speed of said controlled engine until said speed corresponds to the speed of the master engine. As the controlled engine begins to increase in speed, the stator ofthe synchronous motor gradually moves back to its original normally stationary position, said position being reached at the instant when the speed of the controlled engine is the same as that of the master engine.

If the speed of the controlled engine should increase with respect to that of the master engine, the reverse action will take place, namely, the stator ofgthe synchronous motor .will move angularly in an opposite direction to actuate the speed control means of said controlled engine in such a manner as to decrease the speed thereof.

Referring now to the drawings and more particularly to Fig. 1, thereis shown one embodiment of the invention as applied to a multi-engine aircraft which is maintained in flight by three internal combustion engines 4, 5 and 6 which rotate their respective propellers 1, 8 and" 9. Engine 4 is, in the present instance, the center engine and is employed as the master engine, and engines 5. and 6 constitute the port (left) and starboard (right) engines, respectively, the view being from the rear of the engines, and are the controlled engines which are to be controlled by the master engine 4 in order to maintain their speeds in synchronism with said master engine.

2,066,819 trolled engine, there is provided a synchronous Each of theengines is provided with a speed control means such as a fuel supply device for regulating the amount of fuel to said engine to vary the speed thereof. In the form shown, said means are constituted by carburetors III, II and I2 located at engines 4, 5 and 8, respectively. The feed valves of said carburetors are adapted to be actuated in any suitable manner as by means of rods l3, l4 and ",respectively. Since engine 4 is the master engine, the rod II is manually actuated to operate the speed valve of carburetor in in order to establish a predetermined cruising speed at which the aircraft is to be maintained and to which speed the engines It and 6 are to be synchronized. The rods l4 and I! of the enwhich is drivably connected to said engine in any'suitable manner (notshown) forgenerating alternating current the frequency of which corresponds'to the speed of the engine by virtue of the driving connection of the generator to said engine. The field of said generator may be excited from the battery 25 or any other suitable source of direct current, or the generator may be of the type having a stationary armature coil and a rotating field constituted by a rotating permanent bar magnet. At each of the controlled engines 5 and 6 there is provided a relatively small synchronous electric motor, the one for engine 5 being shown at I! and the one for engine 6 being shown at ll.

One of the small synchronous electric motors, namely, motor I1, is shown in sectional detail in Fig. 4 and includes a stator l9 carried on a shaft lila and is relatively stationary but is adapted to rotate under certain conditions as will appear more fully hereinafter. The stator I9 is provided with an alternating current winding shown in Fig. 2 and is supplied with current through collector rings Nb and brushes I90 from generator l6. Cooperating with stator I9 is a rotor 2| carried by the casing 2ld secured to and rotatable with the shaft 2|a which is adapted to be'driven by the engine 5. The rotor 2| is provided with a direct current winding 20 shown in Fig. 2, said winding being supplied with current through slip rings MD and brushes 2lc from the source 25.

Referring now to the circuit diagram of Fig. 2, each of the synchronous motors l1 and I8 consists of a relatively rotatable alternating current winding which is normally stationary and which will be referred to as the armature, and a direct current field winding wound on a rotatable core providing diametrically opposed pole pieces. The alternating current stator, the direct current field winding and the core of the synchronous motor l! are shown at ll, 20, and 2|, respectively. The corresponding elements of. the synchronous motors I8 24, respectively. The direct current windings 20 and 23 are connected, preferably in parallel, to a suitable source of direct current such, for example, as a battery 25, through a switch 26 which will be described more fully hereinafter. The alternating current windings I9 and 22 of said synchronous motors I1 and I8, respectively, are connected, preferably in parallel, to the generator l6 of the master engine through said switch 26 nating current at the winding l9 will be the same as that of the alternating current in windso that the frequency of the alterare shown at 22, 23, and

' motors I1 and I9 are drivably connected in any ing 22, said frequency corresponding to the speed of the master engine 4 which drives the'gene erator IS. The core members 2| and 240i said suitable manner (not shown) to the engines 3 and 6, respectively, so as to be rotated at speeds corresponding to the speeds of the respective engines to which they are connected. Inasmuch as core members 2| and24 are rotatable, the

' produced by the alternating current windings l9 and 22 will also be periodically reversed-at the frequency of the alternating current pro-- duced by the generator 16, which frequency cor-' responds to the speed of the master engine which drives said generator. Therefore, if the controlled engines 5 and 6 are operated at the same speed as the master engine 4 the fields produced by the windings 29 and 23 will be reversed at the same frequency as the fields produced bythe stator windings l9 and 22. Thus the fields of each synchronous motor are in synchronism and no change in phase relation takes place so that said windings l9 and 22 remain stationary. If, however, the speed of engine 5 or that of engine 6 increases or decreases with respect to the speed of the master engine 4, then the speedof rotation of'the members 2| or 24 will increase or decrease correspondingly. thereby correspondingly increasing or decreasing the frequency of reversal of the field produced by the winding 29 or winding 23 with respect to the frequency of reversal of the field produced by the winding i9 or winding 22. When this occurs, then a change in phase relation takes place and thewinding l9 or 22 will move angularly in one direction or another to follow the increase or decrease and in an amount corresponding to the magnitude of the change in phase relation between the associated .windings whereby the change in phase relation may be utilized for the purpose of actuating .the speed control means of the respective controlled engines.

Means are now provided for employing the change in phase relation between the rotating fields in the manner indicated above and, in the form shown, said means comprising a gear memher-21 (Fig, 1) on the synchronous motor l1 and a similar gear member 29 on the synchronous motor |9, said gear members being connected to or driven by the stators l9 and 22, respectively. when relative rotation thereof takes place. The gear members 21 and 29 are arranged to mesh with gear sectors 29 and 39, respectively, which are pivoted at 3| and 32, respectively, for angular movement when actuated by their respective gears 21 and 23. .The gear sector 29 is then connected to the actuating rod, .0! the carburetor H and the gear sector 33 is 'ciirespondingly connected to' the actuating rod I! of the carburetor l2 and in such a manner thatwhen the speeds of the engines 5 and 6 increase with respect to that'of the engine 4, the relative rotation of the stators l9 hereinbefore.

angular movement about said pivot and is procause the gear sectors 29 and 39 to operate therods '|4 and I! to decrease the fuel supply from the carburetors U and |2 and, hence, to decrease the speed of the corresponding engines. On the other hand, when the speed of the engines 5 and 6 decreases with respect to that of the master engine 4, the actuating rods I4 and vided with an insulating extension or arm 35 on which are carried radially spaced arcuate contact strips 36 and 31. Arranged to cooperate with the contact strips 36 and 31 are two pairs of fixed contacts 39, 39 and 40, 4|. The fixed contacts 38 and 39 are adapted to be bridged by the contact strip 36 and the fixed contacts 49, 4f are adapted to be bridged by the contact strip '37 when the handle member 33 is moved substantially ninety degrees in a counter clockwise direction, as is indicated by the arrow,- thereby placing the switch in an on position from the "011 position in which it was before. The contact 33 is connected by-means of a lead 42 to a lead 43 which connects one end of each of the field windings 20 and 23 together. The contact 39 is connected by means of a lead 44 to one side of the'battery and the other side of said battery is connected by means of a lead 45 to a lead 49 which connects the other ends of the windings 29, 23 together, thereby connecting said windings in parallel with the battery 25 when the contact strip 36 bridges the contacts 33, 39.

Contact 49 is connected by means of a lead 41 to a lead 43 which connects one of the ends of the armature windings l9- and 22 together and the contact 4| is connected by means of a lead 49 to one terminal of the alternating current generator IS; The other terminal of generator I 6 is connected by means of a lead 59 to a lead 5| which connects the other ends-of the armature windings l9 and 22 together so that said windings are connected in parallel with the generator I through the contacts 49 and 4| when the latter are bridged by the contact strip 31 of the switch 26;

Means are also provided, it desired, whereby the automatlc control of the controlled engines may be rendered ineflective and each engine controlled individually by separate manual controls. Preferably, such means are made to operate simultaneously with the switch 29 so that when the latter is in an "of!" position the separate manual controls of the engines can be operated individually only and when the switch is in the on" position, the individual manual controls of the controlled engines are connected to their respective engines in such a manner that they will not interfere with the automatic control and will be operated in synchronism with the master control mechanism. 7

One embodiment of such switching means is and 22 of the synchronous motors l1 and II will by the automatic control shown in Fig. 3' or the dram and, in the 7-5 form illustrated, includes a pulley 82 provided at the carburetor ill of the master engine, said pulley being substituted for the control rod l8 shown in Fig. 1." Corresponding pulleys 88 and 88 are provided at the carburetors ll, l2 of the port and starboard engines, respectively. These pulleys, however, are provided in addition to the actuating rods H and I5 which are automatically operated by the armatures ofthe synchronous motors l1 and I8, respectively.

The pulleys 82, 88 and 84 are adapted to be manually operated by'means of throttle levers 88, 88 and 81, respectively, which are located at some'convenient place within reach of the pilot of the aircraft, and for this purpose said pulleys 82, 88 and 84 are connectedby means of endless cables 88, 88 and 88, respectively, topulleys 8i, 82 and 88, respectively, to which are secured the respective throttle levers 55, 88 and 81 in any suitable manner as by means of screws which engage tubular extensions provided on said pulleys as shown in the cross-sections of pulleys pulleys 82 and 88 from the journal heads 84 and 88, respectively, said pulleys 82 and 88 and their associated journal heads 88 and 88, having friction surfaces which-are adapted to engage as shown at H and 12. The pulley 8| also frictionaliy engages its associated journal head 85 as shown at N.

The pulley 8| which is connected to the pulley 82 of the carburetor ll of the master engine is held in frictional engagement with its associated journal head 88 by means of a compression coil spring I! interposed between'the journal head 88 and the throttle lever 88 so that when said throttle lever 88 is moved angularly on the shaft or rod 18 it will remain in any position into which it is moved. Pulleys 82 and 88 are likewise held in frictional engagement with their cooperating journal heads 84 and 88 by means of coil springs "and II, respectively, spring I8 being interposed between a flange I8 and the end ofv a yoke member I8 carried by rod I8, while the spring 11 is interposed between a corresponding flange 88 and a collar 8| secured to the shaft or rod I8.

Means are now provided for longitudinally moving the friction control rod 18 to reduce the friction between the pulleys 82, 88 and their associated journal heads 84 and 88 when the control rods I8 and II are to be actuated automatically by the synchronous motors I1 .and I 8, thereby permitting said pulleys 82 and 88 to freely rotate on the rod I8 and hence to permit the throttle levers 88 and 81 which are connected thereto to follow the movements of the pulleys 88 and 84 as they are actuated by the control rods I8 and I! in order to insure that said throttle levers 88 and 81 will be free to assume positions corresponding to the position of the lever 88 which is a link 82 which is pivotally connected at one end to the yoke I8 and at its other end to a manually operable lever 88 which is pivoted at 88, said yoke 19 being connected to one end of the rod III by means of the pin 85. A toggle spring 88 is provided, one end of which isconnected to .a

pin 81 carried by the lever 88 and the other end of which is connected to a fixed pin 88 carried by a casing 88, within which the switch 28 shown in Fig. 2 and described hereinbefore, is located, said casing being carried by the support 88. Stops 8| and 82 are provided on the casing 89, which serve to limit the angular movement of the lever 88 between the off and the on positions of said lever.

The position in which the lever 88 is shown in Fig. 3 is the of! position and at this time the rod 18 is at the limit of its longitudinal movement to the right thereby causing the coil springs 18 and TI to press the pulleys 82 and 88 into firm frictional engagement with their associated journal heads 84 and 88 by means of the flanges 18 and 88 so that the throttle levers 58 and 51 can be actuated only manually by the operator or pilot in order to overcome the friction at the surfaces" and 12. When, however, the lever 88 is moved downwardly, as viewed in Fig. 3, to the on position shown in dotted lines, the link 82 is moved upwardly to the position shown, thereby actuating the rod 18 to the left so that the pressure of the springs 18 and TI on the flanges 18 and 88 is substantially reduced, consequently reducing the friction between the pulleys 82, 88 and their cooperating journal heads 84 and 88. When the friction of the pulleys 82 and 88 is thus reduced they are substantially free to follow the movements of the pulleys 58 and 54 to which they are connected and thereby permit the throttle levers 88 and 81 to assume positions corresponding to the position of the manually operated throttle lever 85 which is the only one operated by the pilot when the lever 88 is in the "on position because at this time the carburetors II and I2 are controlled automatically by the control. rods l8 and I8.

In order that the circuits of the synchronous motors l1 and I8 may be rendered ineffective at the same time that it is desired to actuate'the throttle levers 88 and 81 manually, the lever 88 is connected to the arm 88 of the switch 28 in any suitable manner (not shown), said switch 28, as previously stated, being housed within the case of 88. A handle member 88 is provided on the lever 88 for moving the lever 88 into the off" and "on positions and, hence, for simultaneously actuating the arm 88 of the switch 28.

There is thus provided, in accordance with the invention, a-novel electrical apparatus for automatically controlling the speed of the engines of a multi-engine aircraft to maintain the propellers thereof in synchronism by automatically controlling the fuel supply means of those engines which are to be synchronized with a master engine, the speed of the latter being controlled by manual operation of its fuel supp means. Novel means are also provided whereby the automatic control can be readily and quickly rendered inoperative when desired and the speed of each engine controlled manually and individually.

Although only one embodiment of the invention has been illustrated and described, various changes and modifications which will now appear to those skilled in the art may be made without departing from the general scope of the invenof the invention.

What is claimed is:'

1. In a multi-engine aircraft having a master engine and a controlled engine, each driving a respective propeller for maintaining the craft in flight, apparatus for automatically synchronizing said engines and their respective propel-.

lers, comprising an electric motor at the controlledengine and having a pair of relatively rotatable coils, means operated by the master engine for causing one of said coils to produce a reversing magnetic field which reverses in accordance with the speed of said master engine,

means operated by th controlled engine for causing the other coil to produce a reversing field which reverses in accordance with the speed of said controlled engine, whereby relative rotation takes place between said coils due to a change in phase relation produced between the two fields by a diflference in speed of the two engines, and means actuated by the relative rotation of said coils for regulating the speed of the controlled engine to that of the master engine whereby saidengines and theirrespective coils, means operated by the master engine for causing one of saidcoils to produce a reversing magnetic field which reverses in accordance with the speed'of saidv master engine,- means operated by the controlled engine for causing the other coil to produce areversing field which reverses in accordance with the speed of said controlled engine, whereby relative rotation takes place be-' tween said coils due to a change in phase relation produced between the two fields by a difference in speed of the two engines, and means actuated by the relative rotation of said coils for regulating the speed of the controlled engine to that of the master engine whereby said. en-

' gines and their respective propellers are mainmeans located within reach, of the pilot of the craft when the latter is in flight for rendering tained in synchronism, and manually operable the automatic control apparatus ineffective 7 whereby the speed or each engine may be controlled individually by the pilot.

3. In an aircraft having a plurality of propellers which are required to rotate in fixed speed relation, each propeller having an engine for driving it including means for controlling the speed thereof, manually operable means for actuating the speed controlling means 01' one of said engines, and automatically operable means for actuating the speed controlling means of the other engines to maintain the speeds or the': latter in synchronism with the first engine and comprising a member at each of saidother engines and driven thereby, and a cooperating rreely movable member for each of said driven members; one of each pair of said members providing magnetic poles of fixed polarity and the other of each pair oisaid members having a winding adapted to be energizedby an alternating; current to provide an alternating current field cooperating with the poles or fixed polarity, andmeans operated by the first engine for generating and supplying an alterating current for each of said windings at a frequency corresponding to the speed of said first engine.

4. In an aircraft having a plurality of propellers which are required to rotate in fixed speed relation, each propeller having an engine for driving it including means for controlling the speed thereof, manually operable means for actuating the speed controlling means of one of said engines, and automatically operable means for actuating the speed controlling means of the other engines to maintain the speeds of the latter in synchronism with the first engine and comprising a member at each of said other engines and driven thereby, and a cooperating free: ly movable member for each of said driven members, one of each pair of said members providing magnetic poles of fixed polarity and the other of each pair of said members having a winding adapted to be energized by an'alternating current to provide an alternating current field cooperating with the poles of fixed polarity, and means operated by the first engine for generating and supplying an alternating current to each of said windings" at a frequency corresponding to the speed of said first engine, and manually operable means for simultaneously disconnecting the automatically operable means from said other engines and for cutting off the supply of alternating current to said windings whereby said other engines may be operated individually and independently of the first engine.

5. In a multi-engine aircraft having a master engine and a controlled engine, each driving a respective propeller for maintaining the craft in flight, apparatus for automatically synchronizing said engines and their respective propellers, comprising an electric motor at the controlled engine and having a pair of windings, means operated by the master engine for causing one of said windings to produce a reversing magnetic field which reverses in accordance with the speed of i said master engine, means operated by the controlled engine for causing the other winding to produce a reversing magnetic field which reverses in accordancewith the speed of said controlled engine, whereby relative rotation takes place between said windings due to a change in phase relation produced between the two fields by a difference in speed of the two engines, and

means actuated by such relative rotation for regulating the speed of the controlled engine to' that of the master engine whereby said engines and their respective propellers are maintained in synchronism.

WILLIAM S. BERRY. 

